Mitigating wind turbine blade noise generation in response to an atmospheric variation

ABSTRACT

Described embodiments include a wind turbine system. In this embodiment, the system includes a rotor blade attached to a rotor hub drivingly coupled to an electric generator. The system includes a controllable feature configured to decrease a noise generated by the rotor blade if activated. The system includes a sensor configured to detect an atmospheric variation approaching the rotor blade. The system includes a noise manager circuit configured to authorize a noise mitigation measure responsive to the detected atmospheric variation. The system includes a control circuit configured to activate the controllable feature in response to the authorized noise mitigation measure. In an embodiment, the system includes a support structure positioning the rotor hub a sufficient distance above the ground to allow rotation of the rotor blade about the rotor hub without contacting the ground.

If an Application Data Sheet (ADS) has been filed on the filing date ofthis application, it is incorporated by reference herein. Anyapplications claimed on the ADS for priority under 35 U.S.C. §§119, 120,121, or 365(c), and any and all parent, grandparent, great-grandparent,etc. applications of such applications, are also incorporated byreference, including any priority claims made in those applications andany material incorporated by reference, to the extent such subjectmatter is not inconsistent herewith.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to and/or claims the benefit of theearliest available effective filing date(s) from the following listedapplication(s) (the “Priority Applications”), if any, listed below(e.g., claims earliest available priority dates for other thanprovisional patent applications or claims benefits under 35 USC §119(e)for provisional patent applications, for any and all parent,grandparent, great-grandparent, etc. applications of the PriorityApplication(s)). In addition, the present application is related to the“Related Applications,” if any, listed below.

PRIORITY APPLICATIONS

None

RELATED APPLICATIONS

U.S. patent application Ser. No. 13/681,196, entitled MITIGATING WINDTURBINE BLADE NOISE GENERATION, naming William D. Duncan, Roderick A.Hyde, David B. Tuckerman, and Lowell L. Wood, Jr., as inventors, filedNov. 19, 2012, is related to the present application.

U.S. patent application Ser. No. 13/681,266, entitled MITIGATING WINDTURBINE BLADE NOISE GENERATION IN VIEW OF A MINIMUM POWER GENERATIONREQUIREMENT, naming William D. Duncan, Roderick A. Hyde, David B.Tuckerman, and Lowell L. Wood, Jr., as inventors, filed Nov. 19, 2012,is related to the present application.

The United States Patent Office (USPTO) has published a notice to theeffect that the USPTO's computer programs require that patent applicantsreference both a serial number and indicate whether an application is acontinuation, continuation-in-part, or divisional of a parentapplication. Stephen G. Kunin, Benefit of Prior-Filed Application, USPTOOfficial Gazette Mar. 18, 2003. The USPTO further has provided forms forthe Application Data Sheet which allow automatic loading ofbibliographic data but which require identification of each applicationas a continuation, continuation-in-part, or divisional of a parentapplication. The present Applicant Entity (hereinafter “Applicant”) hasprovided above a specific reference to the application(s) from whichpriority is being claimed as recited by statute. Applicant understandsthat the statute is unambiguous in its specific reference language anddoes not require either a serial number or any characterization, such as“continuation” or “continuation-in-part,” for claiming priority to U.S.patent applications. Notwithstanding the foregoing, Applicantunderstands that the USPTO's computer programs have certain data entryrequirements, and hence Applicant has provided designation(s) of arelationship between the present application and its parentapplication(s) as set forth above and in any ADS filed in thisapplication, but expressly points out that such designation(s) are notto be construed in any way as any type of commentary and/or admission asto whether or not the present application contains any new matter inaddition to the matter of its parent application(s).

If the listings of applications provided above are inconsistent with thelistings provided via an ADS, it is the intent of the Applicant to claimpriority to each application that appears in the Priority Applicationssection of the ADS and to each application that appears in the PriorityApplications section of this application.

All subject matter of the Priority Applications and the RelatedApplications and of any and all parent, grandparent, great-grandparent,etc. applications of the Priority Applications and the RelatedApplications, including any priority claims, is incorporated herein byreference to the extent such subject matter is not inconsistentherewith.

SUMMARY

For example, and without limitation, an embodiment of the subject matterdescribed herein includes a wind turbine system. In this embodiment, thewind turbine system includes a rotor blade attached to a rotor hubdrivingly coupled to an electric generator. The system includes acontrollable feature configured to decrease a noise generated by therotor blade if activated. The system includes a sensor configured todetect an atmospheric variation approaching the rotor blade. The systemincludes a noise manager circuit configured to authorize a noisemitigation measure responsive to the detected atmospheric variation. Thesystem includes a control circuit configured to activate thecontrollable feature in response to the authorized noise mitigationmeasure. In an embodiment, the system includes a support structurepositioning the rotor hub a sufficient distance above the ground toallow rotation of the rotor blade about the rotor hub without contactingthe ground.

For example, and without limitation, an embodiment of the subject matterdescribed herein includes a method. In this embodiment, the methodincludes detecting an atmospheric variation approaching a rotating rotorblade having a controllable feature and attached to a rotor hub drivingan electric generator. The controllable feature is configured todecrease a noise generated by the rotor blade if activated. The methodincludes authorizing a noise mitigation measure responsive to thedetected atmospheric variation. The method includes activating thecontrollable feature of the rotating rotor blade in response to theauthorized noise mitigation measure. In an embodiment, the methodincludes predicting an arrival of the approaching atmospheric variationat the rotating rotor blade. In an embodiment, the activating includesactivating the controllable feature of the rotating rotor blade inresponse to the authorized noise mitigation measure and in response tothe predicted arrival of the atmospheric variation.

For example, and without limitation, an embodiment of the subject matterdescribed herein includes a system. In this embodiment, the systemincludes means for detecting an atmospheric variation approaching arotating rotor blade having a controllable feature and attached to arotor hub driving an electric generator. The controllable feature isconfigured to decrease a noise generated by the rotor blade ifactivated. The system includes means for authorizing a noise mitigationmeasure responsive to the detected atmospheric variation. The systemincludes means for activating the controllable feature of the rotatingrotor blade in response to the authorized noise mitigation measure. Inan embodiment, the system includes means for predicting an arrival ofthe approaching atmospheric variation at the rotating rotor blade.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example embodiment of a thin computing device 19;

FIG. 2 illustrates an example embodiment of a general-purpose computingsystem 100;

FIG. 3 illustrates an example environment 200;

FIG. 4 illustrates an example operational flow 300;

FIG. 5 illustrates an example environment 400;

FIG. 6 illustrates an example operational flow 500;

FIG. 7 illustrates an alternative embodiment of the operational flow 500described in conjunction with FIG. 6;

FIG. 8 illustrates an alternative embodiment of the operational flow 500described in conjunction with FIG. 6;

FIG. 9 illustrates an example environment 600;

FIG. 10 illustrates an example operational flow 700;

FIG. 11 illustrates an alternative embodiment of the operational flow700 of FIG. 10;

FIG. 12 illustrates an alternative embodiment of the operational flow700 of FIG. 10;

FIG. 13 illustrates an alternative embodiment of the operational flow700 of FIG. 10;

FIG. 14 illustrates an example system 800;

FIG. 15 illustrates an example environment 900;

FIG. 16 illustrates an example operational flow 1000; and

FIG. 17 illustrates an example operational flow 1100.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here.

Those having skill in the art will recognize that the state of the arthas progressed to the point where there is little distinction leftbetween hardware, software, and/or firmware implementations of aspectsof systems; the use of hardware, software, and/or firmware is generally(but not always, in that in certain contexts the choice between hardwareand software can become significant) a design choice representing costvs. efficiency tradeoffs. Those having skill in the art will appreciatethat there are various vehicles by which processes and/or systems and/orother technologies described herein can be effected (e.g., hardware,software, and/or firmware), and that the preferred vehicle will varywith the context in which the processes and/or systems and/or othertechnologies are deployed. For example, if an implementer determinesthat speed and accuracy are paramount, the implementer may opt for amainly hardware and/or firmware vehicle; alternatively, if flexibilityis paramount, the implementer may opt for a mainly softwareimplementation; or, yet again alternatively, the implementer may opt forsome combination of hardware, software, and/or firmware. Hence, thereare several possible vehicles by which the processes and/or devicesand/or other technologies described herein may be effected, none ofwhich is inherently superior to the other in that any vehicle to beutilized is a choice dependent upon the context in which the vehiclewill be deployed and the specific concerns (e.g., speed, flexibility, orpredictability) of the implementer, any of which may vary. Those skilledin the art will recognize that optical aspects of implementations willtypically employ optically-oriented hardware, software, and or firmware.

In some implementations described herein, logic and similarimplementations may include software or other control structuressuitable to implement an operation. Electronic circuitry, for example,may manifest one or more paths of electrical current constructed andarranged to implement various logic functions as described herein. Insome implementations, one or more media are configured to bear adevice-detectable implementation if such media holds or transmits aspecial-purpose device instruction set operable to perform as describedherein. In some variants, for example, this may manifest as an update orother modification of existing software or firmware, or of gate arraysor other programmable hardware, such as by performing a reception of ora transmission of one or more instructions in relation to one or moreoperations described herein. Alternatively or additionally, in somevariants, an implementation may include special-purpose hardware,software, firmware components, and/or general-purpose componentsexecuting or otherwise invoking special-purpose components.Specifications or other implementations may be transmitted by one ormore instances of tangible transmission media as described herein,optionally by packet transmission or otherwise by passing throughdistributed media at various times.

Alternatively or additionally, implementations may include executing aspecial-purpose instruction sequence or otherwise invoking circuitry forenabling, triggering, coordinating, requesting, or otherwise causing oneor more occurrences of any functional operations described below. Insome variants, operational or other logical descriptions herein may beexpressed directly as source code and compiled or otherwise invoked asan executable instruction sequence. In some contexts, for example, C++or other code sequences can be compiled directly or otherwiseimplemented in high-level descriptor languages (e.g., alogic-synthesizable language, a hardware description language, ahardware design simulation, and/or other such similar mode(s) ofexpression). Alternatively or additionally, some or all of the logicalexpression may be manifested as a Verilog-type hardware description orother circuitry model before physical implementation in hardware,especially for basic operations or timing-critical applications. Thoseskilled in the art will recognize how to obtain, configure, and optimizesuitable transmission or computational elements, material supplies,actuators, or other common structures in light of these teachings.

In a general sense, those skilled in the art will recognize that thevarious embodiments described herein can be implemented, individuallyand/or collectively, by various types of electro-mechanical systemshaving a wide range of electrical components such as hardware, software,firmware, and/or virtually any combination thereof and a wide range ofcomponents that may impart mechanical force or motion such as rigidbodies, spring or torsional bodies, hydraulics, electro-magneticallyactuated devices, and/or virtually any combination thereof.Consequently, as used herein “electro-mechanical system” includes, butis not limited to, electrical circuitry operably coupled with atransducer (e.g., an actuator, a motor, a piezoelectric crystal, a MicroElectro Mechanical System (MEMS), etc.), electrical circuitry having atleast one discrete electrical circuit, electrical circuitry having atleast one integrated circuit, electrical circuitry having at least oneapplication specific integrated circuit, electrical circuitry forming ageneral purpose computing device configured by a computer program (e.g.,a general purpose computer configured by a computer program which atleast partially carries out processes and/or devices described herein,or a microprocessor configured by a computer program which at leastpartially carries out processes and/or devices described herein),electrical circuitry forming a memory device (e.g., forms of memory(e.g., random access, flash, read only, etc.)), electrical circuitryforming a communications device (e.g., a modem, module, communicationsswitch, optical-electrical equipment, etc.), and/or any non-electricalanalog thereto, such as optical or other analogs. Those skilled in theart will also appreciate that examples of electro-mechanical systemsinclude but are not limited to a variety of consumer electronicssystems, medical devices, as well as other systems such as motorizedtransport systems, factory automation systems, security systems, and/orcommunication/computing systems. Those skilled in the art will recognizethat electro-mechanical, as used herein, is not necessarily limited to asystem that has both electrical and mechanical actuation except ascontext may dictate otherwise.

In a general sense, those skilled in the art will also recognize thatthe various aspects described herein which can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, and/or any combination thereof can be viewed as being composedof various types of “electrical circuitry.” Consequently, as used herein“electrical circuitry” includes, but is not limited to, electricalcircuitry having at least one discrete electrical circuit, electricalcircuitry having at least one integrated circuit, electrical circuitryhaving at least one application specific integrated circuit, electricalcircuitry forming a general purpose computing device configured by acomputer program (e.g., a general purpose computer configured by acomputer program which at least partially carries out processes and/ordevices described herein, or a microprocessor configured by a computerprogram which at least partially carries out processes and/or devicesdescribed herein), electrical circuitry forming a memory device (e.g.,forms of memory (e.g., random access, flash, read only, etc.)), and/orelectrical circuitry forming a communications device (e.g., a modem,communications switch, optical-electrical equipment, etc.). Those havingskill in the art will recognize that the subject matter described hereinmay be implemented in an analog or digital fashion or some combinationthereof.

Those skilled in the art will likewise recognize that at least some ofthe devices and/or processes described herein can be integrated into adata processing system. Those having skill in the art will recognizethat a data processing system generally includes one or more of a systemunit housing, a video display device, memory such as volatile ornon-volatile memory, processors such as microprocessors or digitalsignal processors, computational entities such as operating systems,drivers, graphical user interfaces, and applications programs, one ormore interaction devices (e.g., a touch pad, a touch screen, an antenna,etc.), and/or control systems including feedback loops and controlmotors (e.g., feedback for sensing position and/or velocity; controlmotors for moving and/or adjusting components and/or quantities). A dataprocessing system may be implemented utilizing suitable commerciallyavailable components, such as those typically found in datacomputing/communication and/or network computing/communication systems.

FIGS. 1 and 2 provide respective general descriptions of severalenvironments in which implementations may be implemented. FIG. 1 isgenerally directed toward a thin computing environment 19 having a thincomputing device 20, and FIG. 2 is generally directed toward a generalpurpose computing environment 100 having general purpose computingdevice 110. However, as prices of computer components drop and ascapacity and speeds increase, there is not always a bright line betweena thin computing device and a general purpose computing device. Further,there is a continuous stream of new ideas and applications forenvironments benefited by use of computing power. As a result, nothingshould be construed to limit disclosed subject matter herein to aspecific computing environment unless limited by express language.

FIG. 1 and the following discussion are intended to provide a brief,general description of a thin computing environment 19 in whichembodiments may be implemented. FIG. 1 illustrates an example systemthat includes a thin computing device 20, which may be included orembedded in an electronic device that also includes a device functionalelement 50. For example, the electronic device may include any itemhaving electrical or electronic components playing a role in afunctionality of the item, such as for example, a refrigerator, a car, adigital image acquisition device, a camera, a cable modem, a printer, anultrasound device, an x-ray machine, a non-invasive imaging device, oran airplane. For example, the electronic device may include any itemthat interfaces with or controls a functional element of the item. Inanother example, the thin computing device may be included in animplantable medical apparatus or device. In a further example, the thincomputing device may be operable to communicate with an implantable orimplanted medical apparatus. For example, a thin computing device mayinclude a computing device having limited resources or limitedprocessing capability, such as a limited resource computing device, awireless communication device, a mobile wireless communication device, asmart phone, an electronic pen, a handheld electronic writing device, ascanner, a cell phone, a smart phone (such as an Android® or iPhone®based device), a tablet device (such as an iPad®), or a Blackberry®device. For example, a thin computing device may include a thin clientdevice or a mobile thin client device, such as a smart phone, tablet,notebook, or desktop hardware configured to function in a virtualizedenvironment.

The thin computing device 20 includes a processing unit 21, a systemmemory 22, and a system bus 23 that couples various system componentsincluding the system memory 22 to the processing unit 21. The system bus23 may be any of several types of bus structures including a memory busor memory controller, a peripheral bus, and a local bus using any of avariety of bus architectures. The system memory includes read-onlymemory (ROM) 24 and random access memory (RAM) 25. A basic input/outputsystem (BIOS) 26, containing the basic routines that help to transferinformation between sub-components within the thin computing device 20,such as during start-up, is stored in the ROM 24. A number of programmodules may be stored in the ROM 24 or RAM 25, including an operatingsystem 28, one or more application programs 29, other program modules 30and program data 31.

A user may enter commands and information into the computing device 20through one or more input interfaces. An input interface may include atouch-sensitive display, or one or more switches or buttons withsuitable input detection circuitry. A touch-sensitive display isillustrated as a display 32 and screen input detector 33. One or moreswitches or buttons are illustrated as hardware buttons 44 connected tothe system via a hardware button interface 45. The output circuitry ofthe touch-sensitive display 32 is connected to the system bus 23 via avideo driver 37. Other input devices may include a microphone 34connected through a suitable audio interface 35, or a physical hardwarekeyboard (not shown). Output devices may include the display 32, or aprojector display 36.

In addition to the display 32, the computing device 20 may include otherperipheral output devices, such as at least one speaker 38. Otherexternal input or output devices 39, such as a joystick, game pad,satellite dish, scanner or the like may be connected to the processingunit 21 through a USB port 40 and USB port interface 41, to the systembus 23. Alternatively, the other external input and output devices 39may be connected by other interfaces, such as a parallel port, game portor other port. The computing device 20 may further include or be capableof connecting to a flash card memory (not shown) through an appropriateconnection port (not shown). The computing device 20 may further includeor be capable of connecting with a network through a network port 42 andnetwork interface 43, and through wireless port 46 and correspondingwireless interface 47 may be provided to facilitate communication withother peripheral devices, including other computers, printers, and so on(not shown). It will be appreciated that the various components andconnections shown are examples and other components and means ofestablishing communication links may be used.

The computing device 20 may be primarily designed to include a userinterface. The user interface may include a character, a key-based, oranother user data input via the touch sensitive display 32. The userinterface may include using a stylus (not shown). Moreover, the userinterface is not limited to an actual touch-sensitive panel arranged fordirectly receiving input, but may alternatively or in addition respondto another input device such as the microphone 34. For example, spokenwords may be received at the microphone 34 and recognized.Alternatively, the computing device 20 may be designed to include a userinterface having a physical keyboard (not shown).

The device functional elements 50 are typically application specific andrelated to a function of the electronic device, and are coupled with thesystem bus 23 through an interface (not shown). The functional elementsmay typically perform a single well-defined task with little or no userconfiguration or setup, such as a refrigerator keeping food cold, a cellphone connecting with an appropriate tower and transceiving voice ordata information, a camera capturing and saving an image, orcommunicating with an implantable medical apparatus.

In certain instances, one or more elements of the thin computing device20 may be deemed not necessary and omitted. In other instances, one ormore other elements or resources 52 may be deemed necessary and added tothe thin computing device.

FIG. 2 and the following discussion are intended to provide a brief,general description of an environment in which embodiments may beimplemented. FIG. 2 illustrates an example embodiment of ageneral-purpose computing system in which embodiments may beimplemented, shown as a computing system environment 100. Components ofthe computing system environment 100 may include, but are not limitedto, a general purpose computing device 110 having a processor 120, asystem memory 130, and a system bus 121 that couples various systemcomponents including the system memory to the processor 120. The systembus 121 may be any of several types of bus structures including a memorybus or memory controller, a peripheral bus, and a local bus using any ofa variety of bus architectures. By way of example, and not limitation,such architectures include Industry Standard Architecture (ISA) bus,Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus, also known as Mezzanine bus.

The computing system environment 100 typically includes a variety ofcomputer-readable media products. Computer-readable media may includeany media that can be accessed by the computing device 110 and includeboth volatile and nonvolatile media, removable and non-removable media.By way of example, and not of limitation, computer-readable media mayinclude computer storage media. By way of further example, and not oflimitation, computer-readable media may include a communication media.

Computer storage media includes volatile and nonvolatile, removable andnon-removable media implemented in any method or technology for storageof information such as computer-readable instructions, data structures,program modules, or other data. Computer storage media includes, but isnot limited to, random-access memory (RAM), read-only memory (ROM),electrically erasable programmable read-only memory (EEPROM), flashmemory, or other memory technology, CD-ROM, digital versatile disks(DVD), or other optical disk storage, magnetic cassettes, magnetic tape,magnetic disk storage, or other magnetic storage devices, or any othermedium which can be used to store the desired information and which canbe accessed by the computing device 110. In a further embodiment, acomputer storage media may include a group of computer storage mediadevices. In another embodiment, a computer storage media may include aninformation store. In another embodiment, an information store mayinclude a quantum memory, a photonic quantum memory, or atomic quantummemory. Combinations of any of the above may also be included within thescope of computer-readable media.

Communication media may typically embody computer-readable instructions,data structures, program modules, or other data in a modulated datasignal such as a carrier wave or other transport mechanism and includeany information delivery media. The term “modulated data signal” means asignal that has one or more of its characteristics set or changed insuch a manner as to encode information in the signal. By way of example,and not limitation, communications media may include wired media, suchas a wired network and a direct-wired connection, and wireless mediasuch as acoustic, RF, optical, and infrared media.

The system memory 130 includes computer storage media in the form ofvolatile and nonvolatile memory such as ROM 131 and RAM 132. A RAM mayinclude at least one of a DRAM, an EDO DRAM, a SDRAM, a RDRAM, a VRAM,or a DDR DRAM. A basic input/output system (BIOS) 133, containing thebasic routines that help to transfer information between elements withinthe computing device 110, such as during start-up, is typically storedin ROM 131. RAM 132 typically contains data and program modules that areimmediately accessible to or presently being operated on by theprocessor 120. By way of example, and not limitation, FIG. 2 illustratesan operating system 134, application programs 135, other program modules136, and program data 137. Often, the operating system 134 offersservices to applications programs 135 by way of one or more applicationprogramming interfaces (APIs) (not shown). Because the operating system134 incorporates these services, developers of applications programs 135need not redevelop code to use the services. Examples of APIs providedby operating systems such as Microsoft's “WINDOWS”® are well known inthe art.

The computing device 110 may also include other removable/non-removable,volatile/nonvolatile computer storage media products. By way of exampleonly, FIG. 2 illustrates a non-removable non-volatile memory interface(hard disk interface) 140 that reads from and writes for example tonon-removable, non-volatile magnetic media. FIG. 2 also illustrates aremovable non-volatile memory interface 150 that, for example, iscoupled to a magnetic disk drive 151 that reads from and writes to aremovable, non-volatile magnetic disk 152, or is coupled to an opticaldisk drive 155 that reads from and writes to a removable, non-volatileoptical disk 156, such as a CD ROM. Other removable/non-removable,volatile/non-volatile computer storage media that can be used in theexample operating environment include, but are not limited to, magnetictape cassettes, memory cards, flash memory cards, DVDs, digital videotape, solid state RAM, and solid state ROM. The hard disk drive 141 istypically connected to the system bus 121 through a non-removable memoryinterface, such as the interface 140, and magnetic disk drive 151 andoptical disk drive 155 are typically connected to the system bus 121 bya removable non-volatile memory interface, such as interface 150.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 2 provide storage of computer-readableinstructions, data structures, program modules, and other data for thecomputing device 110. In FIG. 2, for example, hard disk drive 141 isillustrated as storing an operating system 144, application programs145, other program modules 146, and program data 147. Note that thesecomponents can either be the same as or different from the operatingsystem 134, application programs 135, other program modules 136, andprogram data 137. The operating system 144, application programs 145,other program modules 146, and program data 147 are given differentnumbers here to illustrate that, at a minimum, they are differentcopies.

A user may enter commands and information into the computing device 110through input devices such as a microphone 163, keyboard 162, andpointing device 161, commonly referred to as a mouse, trackball, ortouch pad. Other input devices (not shown) may include at least one of atouch sensitive display, joystick, game pad, satellite dish, andscanner. These and other input devices are often connected to theprocessor 120 through a user input interface 160 that is coupled to thesystem bus, but may be connected by other interface and bus structures,such as a parallel port, game port, or a universal serial bus (USB).

A display 191, such as a monitor or other type of display device orsurface may be connected to the system bus 121 via an interface, such asa video interface 190. A projector display engine 192 that includes aprojecting element may be coupled to the system bus. In addition to thedisplay, the computing device 110 may also include other peripheraloutput devices such as speakers 197 and printer 196, which may beconnected through an output peripheral interface 195.

The computing system environment 100 may operate in a networkedenvironment using logical connections to one or more remote computers,such as a remote computer 180. The remote computer 180 may be a personalcomputer, a server, a router, a network PC, a peer device, or othercommon network node, and typically includes many or all of the elementsdescribed above relative to the computing device 110, although only amemory storage device 181 has been illustrated in FIG. 2. The networklogical connections depicted in FIG. 2 include a local area network(LAN) and a wide area network (WAN), and may also include other networkssuch as a personal area network (PAN) (not shown). Such networkingenvironments are commonplace in offices, enterprise-wide computernetworks, intranets, and the Internet.

When used in a networking environment, the computing system environment100 is connected to the network 171 through a network interface, such asthe network interface 170, or to the network 173 through the modem 172,or through the wireless interface 193. The network may include a LANnetwork environment, or a WAN network environment, such as the Internet.In a networked environment, program modules depicted relative to thecomputing device 110, or portions thereof, may be stored in a remotememory storage device. By way of example, and not limitation, FIG. 2illustrates remote application programs 185 as residing on memorystorage device 181. It will be appreciated that the network connectionsshown are examples and other means of establishing communication linkbetween the computers may be used.

In certain instances, one or more elements of the computing device 110may be deemed not necessary and omitted. In other instances, one or moreother elements may be deemed necessary and added to the computingdevice.

FIG. 3 illustrates an example environment 200 in which embodiments maybe implemented. The illustrated environment includes a wind turbinesystem 202. The environment may include other wind turbine systems,illustrated by a wind turbine system 204.

Wind turbines larger than one megawatt of rated power may be a surprisefor many nearby residents by being much louder than expected. The soundsproduced by blades, gearing, and generator may be significantly louderand more noticeable as wind turbine size increases. Long rotor bladescreate a distinctive aerodynamic sound as air shears off the trailingedge or rear portion of the airfoil and tip. The sound character variesfrom a “whoosh” at low wind speeds to “a jet plane that never lands” atmoderate and higher wind speeds. Blade-induced air vortices spinning offthe tip may produce an audible “thump” as each blade sweeps past themast. Thumping can become more pronounced at distance, sometimesdescribed as “sneakers in a dryer,” when sounds from multiple turbinesarrive at a listener's position simultaneously.

Wind turbines often are not synchronized and so thumps may arrivetogether or separately, creating an unpredictable or chaotic acousticpattern. The sounds of large industrial wind turbines may be clearlyaudible for miles. They may be considered intrusive sounds that areuncharacteristic of a natural soundscape.

The wind turbine system 202 includes a wind turbine 203 having a rotorblade 210 attached to a rotor hub 220 drivingly coupled to an electricgenerator 224. For example, the electric generator may be housed in anacelle 226. The system includes a sensor configured to detect arotational position 218 of the rotor blade relative to a surface of theground 290. FIG. 3 illustrates an embodiment where the rotor bladerotates counterclockwise when viewed from a head-on or upwind direction.In another embodiment, the rotor blade may rotate clockwise. In anembodiment, the sensor is illustrated by a sensor 232 carried by therotor blade 210. In an embodiment, the sensor is illustrated by a sensor234 carried by a support structure 240. In an embodiment, the sensor isillustrated by a sensor 236 carried by a structure 242 other than thesupport structure 240. In an embodiment, a rotational position may beexpressed as a linear distance measurement 292 of a tip 212 of the rotorblade above the ground. In an embodiment, the sensor is illustrated by asensor and rotational angle index mark 238 carried on the rotor hub 220.

In an alternative embodiment, the rotational position 218 may beexpressed by a degree of rotation relative to horizontal axis orrelative to vertical axis of the earth. For example, FIG. 5 illustratesa rotation 494 of a rotor 410 relative to a vertical axis, asillustrated by the support structure 440. Continuing with FIG. 3, thewind turbine system 202 includes a noise controller 250 configured toimplement a noise mitigation measure responsive to the detectedrotational position 218 of the rotor blade relative to the surface ofthe ground 290. While the noise controller is illustrated in FIG. 3 ascarried by the nacelle 226, the noise controller may be carried,located, or positioned at any convenient location. For example, thenoise controller may be carried or mounted within the nacelle, onboardsome other portion of the wind turbine, on the support structure 240, oroff-board of the wind turbine.

In an embodiment, the surface of the ground 290 includes a naturallyoccurring surface of the earth, or a surface of an earthen structure,such as a manmade fill or excavation. In an embodiment, the surface ofthe ground includes a surface of the ground closest to a propeller discdescribed by a revolution of the rotor blade 210. For example, see theportion of the ground proximate to the tip 212 referenced by thedistance measurement 292.

In an embodiment, the sensor is configured to detect a descending motionof the tip 212 of the rotor blade 210 relative to the surface of theground 290. In an embodiment, the sensor is configured to detect anascending motion of the tip of the rotor blade relative to the surfaceof the ground. In an embodiment, the sensor is configured to detect amotion of a tip of the rotor blade generally parallel to the surface ofthe ground. In an embodiment, the sensor is configured to detect arotational position 218 of the rotor blade relative to a portion of thesurface of the ground proximate to the structure 240 supporting therotor hub 220. In an embodiment, the sensor is configured to detect arotational position of the rotor blade relative to the structuresupporting the rotor hub. In an embodiment, the sensor is configured todetect a rotor blade angle within the generator. See sensor androtational angle index mark 238. In an embodiment, the sensor includes atrigger indexed to the rotor blade. In an embodiment, the sensorincludes a microphone. In an embodiment, the sensor includes a pressuresensor. In an embodiment, the sensor includes an optical sensor.

In an embodiment, the noise controller 250 is configured to select andimplement a noise mitigation measure responsive to the detectedrotational position 218 of the rotor blade 210. In an embodiment, thenoise mitigation measure includes changing an orientation of at least aportion of the rotor blade. For example, the changing an orientation mayinclude changing a pitch of the entire rotor blade. For example, thechanging an orientation may include changing a pitch of a portion of therotor blade using a controllable feature 262 of the rotor blade. In anembodiment, the noise mitigation measure includes dynamically shapingairflow over at least a portion of a rotor blade. For example, thedynamically shaping airflow may include using the controllable featureof the rotor blade. In an embodiment, the noise mitigation measureincludes releasing air from a region on the rotor blade. For example,the releasing air may occur on the vacuum side or the pressure side ofthe rotor blade using the controllable feature of the rotor blade. In anembodiment, the noise mitigation measure includes creating atranspiration airflow on at least a portion of the rotor blade.Transpiration is a technique in which extra non-physical normal flowsare created on an airfoil surface in order to form a new streamlinepattern such that the surface streamlines no longer follow the airfoilsurface under inviscid flow. For example, the creating a transpirationairflow may include using the controllable feature of the rotor blade.

In an embodiment, the noise mitigation measure is responsive to adetected descending motion of the tip 212 of the rotor blade 210relative to the surface of the ground 290. In an embodiment, the noisemitigation measure is responsive to a detected ascending motion of a tipof the rotor blade relative to the surface of the ground. In anembodiment, the noise mitigation measure is responsive to a detectedrotational position 218 of the rotor blade relative to the surface ofthe ground. In an embodiment, the noise mitigation measure variesasymmetrically depending upon a detected rotational position 218 of therotor blade relative to the surface of the ground. For example, thenoise mitigation measure may change or vary depending on whether therotor blade is descending toward the surface of the ground, parallelingthe surface of the ground, or ascending away from the surface of theground. In an embodiment, the noise mitigation measure is implemented byan apparatus carried on at least a portion of the rotor blade, such asby the controllable feature 262 of the rotor blade. In an embodiment,the controllable feature of the rotor blade includes a dynamicallyshapeable region of the rotor blade located at a first portion of thelongitudinal length of the rotor blade, and the noise mitigation measureis implemented by the dynamically shapeable region. An example of acontrollable feature of a rotor blade is described by U.S. Pat. App. No.2009/0097976, Driver et al., Apr. 16, 2009. In an embodiment, the noisemitigation measure is implemented by a speaker. In an embodiment, thespeaker is carried by the rotor blade, and may be implemented using thecontrollable feature 262. In an embodiment, a speaker 264 is carried bythe support structure 240 supporting the rotor hub 220. In anembodiment, the speaker 266 is carried by a structure 244 other than thesupport structure 240.

In an embodiment, the system 202 further includes another rotor blade216 attached to the rotor hub 220. In an embodiment, the noisemitigation measure is further responsive to a position of the anotherrotor blade with respect to the surface of the ground 290. In anembodiment, the noise mitigation measure is further responsive to aposition of the another rotor blade with respect to the supportstructure 240. In an embodiment, the system further includes the supportstructure 240 mounted on or in the ground and maintaining the rotor huba sufficient distance above the surface of the ground to allow the rotorblade 210 to rotate about the rotor hub without contacting the surfaceof the ground.

FIG. 4 illustrates an example operational flow 300. After a startoperation, the operational flow includes a locating operation 310. Thelocating operation includes detecting a position relative to a surfaceof the ground of a rotating rotor blade of a wind turbine drivenelectric generator. In an embodiment, the locating operation may beimplemented using the sensors 232, 234, 236, or 238 described inconjunction with FIG. 3. An approval operation 320 includes authorizinga noise mitigation measure responsive to the detected position of therotating rotor blade. In an embodiment, the approval operation may beimplemented using the noise manager circuit 650 described in conjunctionwith FIG. 9. An execution operation 330 includes implementing theauthorized noise mitigation measure. In an embodiment, the executionoperation may be implemented using the noise controller 250 described inconjunction with FIG. 3. The operational flow includes an end operation.

In an embodiment, the detecting a position 310 includes detecting aposition of a tip of the rotating rotor blade. In an embodiment, theauthorizing 320 includes authorizing a noise mitigation measureresponsive to the detected position of the tip of the rotating rotorblade. In an embodiment, the detecting a position includes detecting aposition relative to a surface of the ground closest to a propeller discdescribed by the rotating rotor blade of a rotating rotor blade of awind turbine driven electric generator. In an embodiment, the detectinga position includes detecting a rotational position of the rotor blade.For example, a detected position may be expressed in a degree ofrotation about an axis, such as 10 degrees from vertical, such as in afirst descending quadrant, or as 330 degrees from vertical, such as in athird ascending quadrant. In an embodiment, the detecting a positionincludes detecting a descending or an ascending rotational position ofthe tip of the rotor blade.

In an embodiment, the authorized noise mitigation measure includesdynamically shaping airflow over at least a portion of the rotor blade.In an embodiment, the authorized noise mitigation measure includesreleasing air from a region of the rotor blade. For example, the air maybe released from a vacuum side or a pressure side of the rotor blade. Inan embodiment, the authorized noise mitigation measure includes creatinga transpiration airflow on at least a portion of the rotor blade.

In an embodiment, the implementing 330 includes implementing 332 theauthorized noise mitigation measure using an apparatus carried on atleast a portion of the rotor blade. In an embodiment, the implementingincludes implementing 334 the authorized noise mitigation measure usinga speaker. In an embodiment, the speaker is carried by a structuresupporting the rotor hub. In an embodiment, the speaker is carried bycarried by a structure other than a structure supporting the rotor hub.In an embodiment, the implementing includes implementing 336 theauthorized noise mitigation measure using an apparatus not physicallycoupled with a structure supporting the rotor hub.

FIG. 5 illustrates an example environment 400. The environment includesa wind turbine system 402. In an embodiment, the environment includesanother wind turbine system 404. The wind turbine system 402 includes awind turbine 403 having a rotor blade 410 attached to a rotor hub 420drivingly coupled to an electric generator. The wind turbine systemincludes a support structure 440 mounted on or in the ground 290 andmaintaining the rotor hub a sufficient distance above the surface of theground to allow the rotor blade to rotate about the rotor hub withoutcontacting the surface of the ground. The wind turbine system includes asensor configured to detect a rotational position 494 of the rotor bladerelative to the support structure. In an embodiment, the sensor isillustrated by a sensor 432 carried by the rotor blade 410. In anembodiment, the sensor is illustrated by a sensor 434 carried by asupport structure 440. In an embodiment, the sensor is illustrated by asensor 436 carried by a structure 442 other than the support structure440. In an embodiment, the sensor is illustrated by a sensor androtational position index mark 438 carried on the rotor hub 420. Thewind turbine system includes a noise controller 450 configured toimplement a noise mitigation measure responsive to the detectedrotational position of the rotor blade relative to the supportstructure. While the noise controller is illustrated in FIG. 5 as beingcarried by the nacelle 426, the noise controller may be carried,located, or positioned at any convenient location. For example, thenoise controller may be carried or mounted within the nacelle, onboardsome other portion of the wind turbine, on the support structure 440, oroff board of the wind turbine.

In an embodiment, the sensor is configured to detect a position of a tip412 of the rotor blade relative 410 to the support structure 440. In anembodiment, the sensor is configured to detect the rotor blade sweepingpast the support structure. In an embodiment, the sensor is configuredto detect a motion of a tip 412 of the rotor blade generally parallel tothe surface of the ground. In an embodiment, the noise controller 450 isfurther configured to predict when the rotor blade will sweep past thesupport structure, and to further implement the noise mitigation measureresponsive to the predicted sweep of the rotor blade past the supportstructure. For example, the prediction may include informationforecasting or predicting a time until or when the rotor blade willsweep past the support structure. In an embodiment, the noise mitigationmeasure is implemented by a controllable feature 462 located on therotor blade. In an embodiment, the noise mitigation measure isimplemented by an apparatus located on the support structure, such asthe controllable feature 464. For example, the controllable feature maybe configured to emit an air blast or pull a vacuum in a region sweptthrough by the rotor blade. In an embodiment, the noise mitigationmeasure is responsive to the rotor blade sweeping past the supportstructure. In an embodiment, the noise mitigation measure is implementedby an apparatus carried by a structure other than a structure supportingthe rotor hub on the support structure, such as a speaker 466 carried ona structure 444. In an embodiment, the noise mitigation measure isresponsive to a detected tip of the rotor blade sweeping past thesupport structure.

In an embodiment, the noise mitigation measure is response to a detectedrotational position 438 of the rotor blade 410 relative to the supportstructure 440. In addition to being expressed in degrees or quadrants,the rotational position may be expressed as approaching, paralleling, ordeparting the support structure. In an embodiment, the system 402further includes another rotor blade attached to the rotor hub 420. Inan embodiment, the noise mitigation measure is further responsive to aposition of the another rotor blade with respect to the supportstructure 440.

FIG. 6 illustrates an example operational flow 500. After a startoperation, the operational flow includes a locating operation 510. Thelocating operation includes detecting a position relative to a supportstructure of a rotating rotor blade of a wind turbine driven electricgeneration system. The support structure is mounted on or in the groundand maintains the rotor hub a sufficient distance above the surface ofthe ground to allow rotation of the rotor blade about the rotor hubwithout the rotor blade contacting the ground. In an embodiment, thelocating operation may be implemented using at least one of the sensors432, 434, 436, or 438 described in conjunction with FIG. 5. An executionoperation 540 includes implementing a noise mitigation measureresponsive to the detected position of the rotating rotor blade. In anembodiment, the execution operation may be implemented using the noisecontroller 450 described in conjunction with FIG. 5. The operationalflow includes an end operation.

In an embodiment, the detecting includes detecting a position relativeto a support structure of a tip of a rotating rotor blade of a windturbine electric generation system. In an embodiment, the detectingincludes detecting the rotating rotor blade rotating past the supportstructure. For example a tip or a particular portion of the rotatingrotor blade may be detected.

In an embodiment, the operational flow 500 includes an approvaloperation 520 authorizing implementing the noise mitigation measure. Inan embodiment, the operational flow includes a timing operation 530predicting when the rotating rotor blade will pass the supportstructure.

FIG. 7 illustrates an alternative embodiment of the operational flow 500described in conjunction with FIG. 6. In an embodiment, the approvaloperation 520 includes at least one additional operation. The at leastone additional operation may include an operation 522, an operation 524,or an operation 526. The operation 522 includes authorizing theimplementing the noise mitigation measure in response to a noise impactcriteria. The operation 524 includes authorizing the implementing thenoise mitigation measure in response to a time of day criteria. Theoperation 526 includes authorizing the implementing the noise mitigationmeasure in response to an ambient conditions based criteria. Forexample, an ambient conditions based criteria may include an ambientcondition of the wind turbine, or an ambient condition of a potentiallydownwind neighborhood. In an embodiment, the timing operation 530 mayinclude at least one additional operation, such as an operation 532. Theoperation 532 includes predicting when a tip of the rotating rotor bladewill pass the support structure. In an alternative embodiment, thetiming operation may include predicting when a portion of the rotatingrotor blade will pass the support structure. In an embodiment, theexecution operation 540 may include at least one additional operation,such as an operation 542. The operation 542 includes implementing anoise mitigation measure responsive to the detected position of therotating rotor blade and responsive to the predicted passage of therotating rotor blade past the support structure.

FIG. 8 illustrates an alternative embodiment of the operational flow 500described in conjunction with FIG. 6. In an embodiment, the executionoperation 540 may include at least one additional operation. The atleast one additional operation may include an operation 544, anoperation 546, an operation 548, an operation 552, an operation 554, anoperation 556, or an operation 558. The operation 544 includesimplementing a noise mitigation measure using an apparatus located onthe support structure. For example, a noise mitigation measure mayinclude an air blast, or a vacuum in a region swept through by the rotorblade. The operation 546 includes dynamically shaping airflow over atleast a portion of a rotor blade. An operation includes dynamicallyshaping airflow over at least a portion of a rotor blade as the rotorblade rotates past the support structure. An operation includes changingan orientation of at least a portion of the rotating rotor blade. Theoperation 548 includes releasing air from a region of the rotor blade.For example, the air may be released from the vacuum side or thepressure side of the rotating rotor blade. An operation includesreleasing air from a region of the rotor blade as the rotor bladerotates past the support structure. The operation 552 includes creatinga transpiration airflow on at least a portion of the rotor blade. Anoperation includes creating a transpiration airflow on at least aportion of the rotor blade as the rotor blade rotates past the supportstructure. The operation 554 includes implementing a noise mitigationmeasure using an apparatus carried on at least a portion of the rotorblade. The operation 556 includes implementing a noise mitigationmeasure using an apparatus carried by the support structure. Theoperation 558 includes implementing a noise mitigation measure using aspeaker carried by a structure supporting the rotor hub. An operationincludes implementing a noise mitigation measure using a speaker carriedby a structure other than the structure supporting the rotor hub.

FIG. 9 illustrates an example environment 600. The environment includesa wind turbine system 602. In an alternative embodiment, the environmentincludes another wind turbine system 604, and may include a further windturbine system 606.

The wind turbine system 602 includes a wind turbine 603 having a rotorblade 610 attached to a rotor hub 620 drivingly coupled to an electricgenerator 624. The system includes a sensor configured to detect anatmospheric variation 680 approaching the rotor blade 610. Illustratedembodiments of the sensor include a sensor 631 carried by the rotor hub620, a sensor 632 carried by the rotor blade, a sensor 633 carried by anacelle 626, a sensor 634 carried by the structure 640 supporting therotor hub, and a sensor 635 carried by a structure 642 other than thesupport structure 640. The system includes a controllable featureconfigured to decrease a noise generated by the rotor blade ifactivated. Illustrated embodiments of the controllable feature include acontrollable feature 662 carried by the rotor blade, a controllablefeature 664 carried by the support structure 640, and a controllablefeature 666 carried by another structure 644 other than the supportstructure 640.

The system 602 includes a noise manager circuit 650 configured toauthorize a noise mitigation measure responsive to the detectedatmospheric variation 680. While the noise manager system is illustratedin FIG. 9 as carried by the nacelle 626, the noise manager system may becarried, located, or positioned at any convenient location. For example,the noise manager system may be carried or mounted within the nacelle626, onboard some other portion of the wind turbine, on the supportstructure 640, or off-board the wind turbine. The system includes acontrol circuit 670 configured to activate the controllable feature inresponse to the authorized noise mitigation measure. While the controlcircuit is illustrated in FIG. 9 as carried by the nacelle 626, thecontrol circuit may be carried, located, or positioned at any convenientlocation. For example, the control circuit may be carried or mountedwithin the nacelle, onboard some other portion of the wind turbine, onthe support structure, or off-board the wind turbine.

In an embodiment, the system 602 includes a computing device 675configured to predict a possible shift or change in the detectedatmospheric variation as it approaches the rotor blade. For example, thecomputing device may predict that a detected atmospheric pressure dropwill increase or decrease by the time it reaches the rotor blade. Forexample, the computing device may predict that a detected wind speedchange will dissipate by the time it reaches the rotor blade.

In an embodiment, the rotor blade 610 includes the controllable feature662. In an embodiment, the system 602 further includes a supportstructure carrying the controllable feature. In an embodiment, thesupport structure 640 carries the controllable feature 662 and supportsthe rotor hub 620 a sufficient distance above the ground to allowrotation of the rotor blade about the rotor hub without contacting theground 290. In an embodiment, the support structure includes a structure644 carrying the controllable feature 666.

In an embodiment, the sensor includes a laser Doppler anemometer(hereafter “LIDAR”). An example of a LIDAR sensor used to measure windis described by U.S. Pat. App. No. 2009/0046289, Caldwell et al., Feb.19, 2009. Another example of a LIDAR sensor used to measure wind isdescribed by U.S. Pat. App. No. 2006/0140764, Smith et al., Jun. 29,2006. In an embodiment, the sensor includes a rotary cup anemometer. Inan embodiment, the sensor includes a sonic anemometer. In an embodiment,the sensor includes an atmospheric pressure sensor. In an embodiment,the sensor includes a radar sensor. In an embodiment, the sensor iscarried by the rotor hub, a nacelle enclosing the rotor hub, or astructure supporting the rotor hub. In an embodiment, the sensor isconfigured to detect an atmospheric variation approaching the rotorblade at a distance of at least one rotor blade length upwind of therotor hub. In an embodiment, the sensor is carried by a structurepotentially downwind of the rotor hub. While this embodiment may not beillustrated in FIG. 9, a sensor, for example, may be carried by astructure positioned substantially between the wind turbine system 602and a neighborhood or noise-alleviation zone. In an embodiment, thesensor is carried by a structure potentially upwind of the rotor hub,illustrated as by the support structure 642 carrying the sensor 637. Inan embodiment, the sensor is configured to detect an atmosphericvariation 680 approaching the rotor blade within a time frame sufficientfor the noise manager circuit 650 to authorize a noise mitigationmeasure and the controller circuit 670 to implement the noise mitigationmeasure before or as the atmospheric variation affects the rotor blade.In an embodiment, the sensor includes a sensor configured to detect aspatial variation in airflow approaching the rotor blade. For example, aspatial variation may include a vertical or horizontal variationprofile. In an embodiment, the sensor includes a sensor configured todetect a variation in air moisture content, temperature, or density inan airflow approaching the rotor blade. In an embodiment, the detectedatmospheric variation includes a detected transient atmosphericvariation. For example, a detected atmospheric variation may include agust, shift in wind direction, or patch of warm or cold air. In anembodiment, the detected atmospheric variation includes a detected windspeed, a change in wind speed, a wind direction, a change in winddirection, or a wind gradient. For example, a detected wind speedvariation may include a ½, 1, 2, 3, 5 mph wind speed variation over aparticular time, or a directional variation of 2, 5, or 10 degrees overa particular time for example. In an embodiment, the detectedatmospheric variation includes a detected turbulence, temperature, orpressure variation. In an embodiment, the detected atmospheric variationincludes a detected atmospheric variation categorized as possibly havingan affect on generation of the noise by the rotor blade. In anembodiment, the detected atmospheric variation includes a detectedvariation in a wind speed approaching the rotor blade.

In an embodiment, the controllable feature includes anairflow-modifiable region 662 of the rotor blade 610 located at aportion of a longitudinal length of the rotor blade. In an embodiment,the noise mitigation measure includes changing a cross-sectional shapeof the airflow-modifiable region of the rotor blade. In an embodiment,the noise mitigation measure includes controlling airflow over theairflow-modifiable region. In an embodiment, the noise mitigationmeasure includes dynamically altering airflow over theairflow-modifiable region. In an embodiment, the noise mitigationmeasure includes releasing air from the airflow-modifiable region. In anembodiment, the noise mitigation measure includes creating atranspiration airflow through the airflow-modifiable region. In anembodiment, the controllable feature includes a controllable rotor bladepitch. In an embodiment, the noise mitigation measure includes changinga pitch of the rotor blade. In an embodiment, the noise mitigationmeasure is further implemented by a controllable feature 664 carried onthe structure 640 supporting the rotor hub.

In an embodiment, the authorization of the noise mitigation measure isnot responsive to a possible impact of the authorized noise mitigationmeasure on electric power generated by the electric generator 624. Forexample, the authorization may not take into account, or may beindifferent or agnostic to a possible reduction in electricity generatedby the electric generator. In an embodiment, the authorization of thenoise mitigation measure is responsive to a possible impact of theauthorized noise mitigation measure on electric power generated by theelectric generator. In an embodiment, the authorization of the noisemitigation measure includes authorizing the noise mitigation measure ifthe electric power generation reduction is below a threshold level. Forexample, implementation of the noise mitigation measure may beauthorized if the anticipated power generation reduction is less than10% of that currently being generated. In an embodiment, theauthorization of the noise mitigation measure is responsive to a minimumelectric power generation requirement for the wind turbine system. Forexample, implementation of the noise mitigation measure may beauthorized if the power generation is predicted or calculated to remainabove 1 megawatt. In an embodiment, the noise manager circuit is furtherconfigured to select the noise mitigation measure from at least twopossible noise mitigation measures responsive to the detectedatmospheric variation. In an embodiment, the authorizing includesauthorizing a noise mitigation measure selected from at least twopossible noise mitigation measures responsive to the detectedatmospheric variation.

In an embodiment, the noise manager circuit 650 is further configured toselect the noise mitigation measure having the least reduction inelectric power generated by the electric generator 624 from at least twopossible noise mitigation measures responsive to the detectedatmospheric variation 680. In an embodiment, the noise manager circuitis configured to authorize a noise mitigation measure responsive to adetected average wind speed approaching the rotor blade 610 exceeding athreshold wind speed. In an embodiment, the noise manager circuit isconfigured to authorize a noise mitigation measure responsive to adetected variation of atmospheric pressure approaching the rotor bladethat exceeds a threshold criterion. In an embodiment, the noise managercircuit is configured to authorize a noise mitigation measure responsiveto a detected turbulence, air moisture content, air temperature, or airdensity variation approaching the blade.

In an embodiment, the sensor is configured to detect an atmosphericvariation 680 approaching the rotor blade 610 within a time framesufficient for the noise manager circuit 650 to select the noisemitigation measure and for the controller circuit 670 to implement theauthorized noise mitigation measure before or as the atmosphericvariation affects the rotor blade. In an embodiment, the system 602further includes the support structure 640 positioning the rotor hub 620a sufficient distance above the ground 290 to allow rotation of therotor blade about the rotor hub 620 without contacting the ground.

FIG. 10 illustrates an example operational flow 700. After a startoperation, the operational flow includes a locating operation 710. Thelocating operation includes detecting an atmospheric variationapproaching a rotating rotor blade having a controllable feature andattached to a rotor hub driving an electric generator. The controllablefeature is configured to decrease a noise generated by the rotor bladeif activated. In an embodiment, the locating operation may beimplemented using a sensor of the sensors 631-637 described inconjunction with FIG. 9. An approval operation 720 includes authorizinga noise mitigation measure responsive to the detected atmosphericvariation. In an embodiment, the approval operation may be implementedusing the noise manager circuit 650 described in conjunction with FIG.9. An execution operation 740 includes activating the controllablefeature of the rotating rotor blade in response to the authorized noisemitigation measure. In an embodiment, the execution operation may beimplemented using the control circuit 670 described in conjunction withFIG. 9. The operational flow includes an end operation.

In an alternative embodiment, the operational flow 700 includespredicting 730 an arrival of the approaching atmospheric variation atthe rotating rotor blade. In an alternative embodiment, the executionoperation 740 includes activating 742 the controllable feature of therotating rotor blade in response to the authorized noise mitigationmeasure and in response to the predicted arrival of the atmosphericvariation. In an embodiment, the operational flow includescomputationally predicting a possible shift or change in the detectedatmospheric variation as it approaches the rotor blade. In anembodiment, the computationally predicting may be implemented using thecomputing device 675 described in conjunction with FIG. 9.

FIG. 11 illustrates an alternative embodiment of the operational flow700 of FIG. 10. In an embodiment, the locating operation 710 may includeat least one additional embodiment. The at least one additionalembodiment may include an operation 712, an operation 714, an operation716, or an operation 718. The operation 712 includes detecting anatmospheric variation approaching a rotating rotor blade using a LIDARdevice. The operation 714 includes detecting an atmospheric variationapproaching a rotating rotor blade using an anemometer sensor. Theoperation 716 includes detecting an atmospheric variation approaching arotating rotor blade using a radar sensor. The operation 718 includesdetecting an atmospheric variation approaching the rotor blade within atime frame sufficient to activate the controllable feature before or asthe atmospheric variation affects the rotor blade.

FIG. 12 illustrates an alternative embodiment of the operational flow700 of FIG. 10. In an embodiment, the approval operation 720 may includeat least one additional operation. The at least one additional operationmay include an operation 722, an operation 724, an operation 726, or anoperation 728. The operation 722 includes authorizing a noise mitigationmeasure responsive to the detected atmospheric variation and notresponsive to a possible impact of the authorized noise mitigationmeasure on electric power generated by the electric generator. Theoperation 724 includes authorizing a noise mitigation measure responsiveto the detected atmospheric variation and responsive to a possibleimpact of the authorized noise mitigation measure on electric powergenerated by the electric generator. The operation 726 includesauthorizing a noise mitigation measure responsive to the detectedatmospheric variation and responsive to a minimum electric powergeneration requirement assigned to the electric generator. The operation728 includes authorizing a noise mitigation measure selected from atleast two possible noise mitigation measures responsive to the detectedatmospheric variation.

FIG. 13 illustrates an alternative embodiment of the operational flow700 of FIG. 10. In an embodiment, the execution operation 740 mayinclude at least one additional operation. The at least one additionaloperation may include an operation 744 or an operation 746. Theoperation 744 includes activating an airflow-modifiable region of therotor blade in response to the authorized noise mitigation measure. Theoperation 746 includes activating a controllable rotor blade pitch ofthe rotating rotor blade in response to the authorized noise mitigationmeasure.

FIG. 14 illustrates an example system 800. The system includes means 810for detecting an atmospheric variation approaching a rotating rotorblade having a controllable feature and attached to a rotor hub drivingan electric generator. The controllable feature is configured todecrease a noise generated by the rotor blade if activated. The systemincludes means 820 for authorizing a noise mitigation measure responsiveto the detected atmospheric variation. The system includes means 840 foractivating the controllable feature of the rotating rotor blade inresponse to the authorized noise mitigation measure.

In an alternative embodiment, the system 800 includes means 830 forpredicting an arrival of the approaching atmospheric variation at therotating rotor blade.

FIG. 15 illustrates an example environment 900. The illustratedenvironment includes a wind turbine system 902. The environment mayinclude other wind turbine systems, illustrated by a wind turbine system904.

The wind turbine system 902 includes a wind turbine 903 having a rotorblade 910 attached to a rotor hub 920 drivingly coupled to an electricgenerator 924. For example, the electric generator may be housed in anacelle 926. The rotor blade includes a tip 912. The rotor blade has acontrollable feature 962 configured if activated to decrease a noisegenerated by the rotor blade. If activated, the controllable feature hasa negative or adverse consequence on lift generated by the rotor bladeor it increases drag generated by the rotor blade, which correspondinglyresults in a decrease in electric power generated by the electricgenerator. FIG. 15 illustrates an embodiment with the rotor blade 910rotating counterclockwise when viewed from a head-on or upwinddirection.

The wind turbine system 902 includes a sensor configured to detect aparameter indicative of present or possible future noise generationstate of the rotor blade 910. For example, the parameter may include adistinguishing feature of a present or a possible future noisegeneration state of the rotor blade. For example, a parameter indicativeof a present noise generation state may include turbulence forming overa portion of the rotor blade. In an embodiment, the sensor isillustrated by a sensor 932 carried by the rotor blade 910. In anembodiment, the sensor is illustrated by a sensor 934 carried by asupport structure 940. In an embodiment, the sensor is illustrated by asensor 936 carried by a structure 942 other than the support structure940. In an embodiment, the sensor is illustrated by a sensor androtational position index mark 938 carried on the rotor hub 920.

The wind turbine system 902 includes a noise manager circuit 950configured to select a noise mitigation measure responsive to thedetected parameter and in compliance with a minimum electric powergeneration requirement assigned to the wind turbine system. While thenoise manager circuit is illustrated in FIG. 15 as carried by thenacelle 926, the noise manager circuit may be carried, located, orpositioned at any convenient location. For example, the noise managercircuit may be carried or mounted within the nacelle, onboard some otherportion of the wind turbine, on the support structure 940, or off-boardof the wind turbine 903. The wind turbine system includes a controlcircuit 970 configured to activate the controllable feature in responseto the selected noise mitigation measure. While the control circuit isillustrated in FIG. 15 as carried by the nacelle 926, the controlcircuit may be carried, located, or positioned at any convenientlocation. For example, the control circuit may be carried or mountedwithin the nacelle, onboard some other portion of the wind turbine, onthe support structure, or off-board of the wind turbine.

In an embodiment, the controllable feature includes anairflow-modifiable region of the rotor blade located at a portion of alongitudinal length of the rotor blade. In an embodiment, thecontrollable feature includes a controllable rotor blade pitch. In anembodiment, the sensor is configured to detect a vortex induced noise.In an embodiment, the sensor includes a microphone. In an embodiment,the sensor includes a pressure sensor. In an embodiment, the sensorincludes a vibration or an accelerometer sensor.

In an embodiment, the parameter includes a parameter indicative of noisegenerated by airflow across the rotor blade 910. In an embodiment, theparameter includes a parameter indicative of an atmospheric variationapproaching the rotor blade. In an embodiment, the parameter includes aparameter indicative of noise received by a noise-alleviation zone. Inan embodiment, the noise-alleviation zone includes a land area having anoise tolerance rating. For example, a noise tolerance rating may be atleast partially based on the existing land use in the area, history ofadverse noise incidents, time of day, special events, or prevailing winddirection. In an embodiment, the parameter includes a parameterindicative of a noise produced or propagated by airflow across the rotorblade. For example, the parameter may be indicative of noise generatedby airflow across the rotor blade, including vortexes, vibration, andthe like. In an embodiment, the parameter includes a parameterindicative of a noise produced or propagated by unstalled airflow acrossthe rotor blade. In an embodiment, the parameter includes turbulenceinduced noise.

In an embodiment, the minimum electric power generation requirement isresponsive to a time of day. In an embodiment, the minimum electricpower generation requirement is responsive to a weather condition. Forexample, the weather condition may include a current or a predictedweather condition. In an embodiment, the minimum electric powergeneration requirement is responsive to a wind direction. For example,the wind direction may include a current or a predicted wind direction.In an embodiment, the minimum electric power generation requirement isresponsive to a target cumulative electric power generation requirementover a period of time. For example, a target cumulative electric powergeneration requirement may include a certain number of megawattsgenerated over 12 hours for example, i.e. if target is reached, thenauthorized to cut electric power generation, even to zero; if target isnot reached, system can cut electric power generation but only down toamount predicted to reach target cumulative electric power generationrequirement. In an embodiment, the minimum electric power generationrequirement includes a maximum allowable percentage reduction in presentelectric power generation. For example, if present or target electricpower generation is 2 MW for the wind turbine system 903, the selectednoise mitigation measure cannot reduce the power generation by more than10% or 200 KW. In an embodiment, the minimum electric power generationrequirement is responsive to minimum a monetary value of electric powergeneration over a period of time. For example, the wind turbine musthave generated a minimum dollar value worth of electric power in thelast 24 hours before electric power generation can be reduced or ceased.For example, the dollar value may be computed according to a generallyprevailing price of electricity, or according to spot price ofelectricity. In an embodiment, the minimum electric power generationrequirement is responsive to a noise sensitivity of a noise-alleviationzone lying potentially downwind of the wind turbine.

In an embodiment, the noise mitigation measure is selected in responseto instantaneous values of the detected parameter. In an embodiment, thenoise mitigation measure is selected in response to an average value ofthe detected parameter over a period of time. In an embodiment, thenoise mitigation measure is selected in response to cumulative values ofthe detected parameter and of cumulative power generation over a periodof time. In an embodiment, the noise mitigation measure is selected inresponse to weighted values of the detected parameter and electric powergeneration over a period of time. For example, electric power generationmay be more important at some times of a day than other times.

In an embodiment, the noise mitigation measure includes changing anorientation of a portion of the rotor blade 910. In an embodiment, thenoise mitigation measure includes dynamically shaping airflow over atleast a portion of the rotor blade 910. In an embodiment, the noisemitigation measure includes releasing air from a region on the rotorblade. In an embodiment, the noise mitigation measure includes creatinga transpiration airflow on at least a portion of the rotor blade.

Another embodiment includes a system comprising a first wind turbine anda second wind turbine. The first wind turbine includes a first rotorblade having a first controllable feature and attached to a first rotorhub drivingly coupled to a first electric generator. The firstcontrollable feature is configured if activated to decrease a firstnoise generated by the first rotor blade and correspondingly to decreasea first electric power generated by the first electric generator. Forexample, the first wind turbine may be illustrated by the wind turbinedescribed in conjunction with FIG. 15. The second wind turbine includesa second rotor blade having a second controllable feature and attachedto a second rotor hub drivingly coupled to a second electric generator.The second controllable feature is configured if activated to decrease asecond noise generated by the second rotor blade and correspondingly todecrease a second electric power generated by the second electricgenerator. For example, the second wind turbine may also be illustratedby the wind turbine described in conjunction with FIG. 15.

The system includes a sensor configured to detect a parameter indicativeof present or possible future noise generation state of the first rotorblade or of the second rotor blade. For example, the sensor may includeone of more of the embodiments of the sensor described in conjunctionwith FIG. 15.

The system includes a noise manager circuit configured to select a noisemitigation measure. The noise mitigation measure is selected (i) inresponse to the detected parameter and (ii) in compliance with the firstminimum electric power generation requirement assigned to the firstelectric generator or the second minimum power generation requirementassigned to the second electric generator. For example, the noisemanager circuit may include one of more of the embodiments of the noisemanager circuit 950 described in conjunction with FIG. 15.

The system includes a control system configured to activate the firstcontrollable feature or second controllable feature in response to theselected noise mitigation measure. For example, the control system mayinclude one of more of the embodiments of the control circuit 970described in conjunction with FIG. 15

FIG. 16 illustrates an example operational flow 1000. After a startoperation, the operational flow includes a sensing operation 1010. Thesensing operation includes detecting a parameter indicative of presentor possible future noise generation state of a rotating rotor bladehaving a controllable feature and attached to a rotor hub driving anelectric generator. The controllable feature is configured to decrease anoise generated by the rotating rotor blade if activated. In anembodiment, the sensing operation may be implemented using an embodimentof the sensor described in conjunction with FIG. 15. A choosingoperation 1020 includes selecting a noise mitigation measure responsiveto the detected parameter and in compliance with a minimum electricpower generation requirement assigned to the electric generator. In anembodiment, the choosing operation may be implemented using the noisemanager circuit 950 described in conjunction with FIG. 15. An executionoperation 1030 includes activating the controllable feature of therotating rotor blade in response to the selected noise mitigationmeasure. In an embodiment, the execution operation may be implementedusing the control circuit 970 described in conjunction with FIG. 15. Theoperational flow includes an end operation.

FIG. 17 illustrates an example operational flow 1100. After a startoperation, the operational flow includes a sensing operation 1110. Thesensing operation includes detecting a parameter indicative of presentor possible future noise generation state of each rotating rotor bladeof at least two rotating rotor blades. Each rotating rotor bladerespectively having a controllable feature and is attached to arespective rotor hub driving a respective electric generator. Eachcontrollable feature is configured to decrease a noise generated by itsrespective rotating rotor blade if activated. In an embodiment, thesensing operation may be implemented using an embodiment of the sensordescribed in conjunction with FIG. 15. A choosing operation 1120includes selecting a noise mitigation measure (i) responsive to thedetected parameter and (ii) in compliance with a minimum electric powergeneration requirement assigned to each electric generator of therespective electric generators. In an embodiment, the choosing operationmay be implemented using the noise manager circuit 950 described inconjunction with FIG. 15. An execution operation 1130 includesactivating a controllable feature of a rotating rotor blade of the atleast two rotating rotor blades as appropriate to implement the selectednoise mitigation measure. In an embodiment, the execution operation maybe implemented using the control circuit 970 described in conjunctionwith FIG. 15. The operational flow includes an end operation.

All references cited herein are hereby incorporated by reference intheir entirety or to the extent their subject matter is not otherwiseinconsistent herewith.

In some embodiments, “configured” includes at least one of designed, setup, shaped, implemented, constructed, or adapted for at least one of aparticular purpose, application, or function.

It will be understood that, in general, terms used herein, andespecially in the appended claims, are generally intended as “open”terms. For example, the term “including” should be interpreted as“including but not limited to.” For example, the term “having” should beinterpreted as “having at least.” For example, the term “has” should beinterpreted as “having at least.” For example, the term “includes”should be interpreted as “includes but is not limited to,” etc. It willbe further understood that if a specific number of an introduced claimrecitation is intended, such an intent will be explicitly recited in theclaim, and in the absence of such recitation no such intent is present.For example, as an aid to understanding, the following appended claimsmay contain usage of introductory phrases such as “at least one” or “oneor more” to introduce claim recitations. However, the use of suchphrases should not be construed to imply that the introduction of aclaim recitation by the indefinite articles “a” or “an” limits anyparticular claim containing such introduced claim recitation toinventions containing only one such recitation, even when the same claimincludes the introductory phrases “one or more” or “at least one” andindefinite articles such as “a” or “an” (e.g., “a receiver” shouldtypically be interpreted to mean “at least one receiver”); the sameholds true for the use of definite articles used to introduce claimrecitations. In addition, even if a specific number of an introducedclaim recitation is explicitly recited, it will be recognized that suchrecitation should typically be interpreted to mean at least the recitednumber (e.g., the bare recitation of “at least two chambers,” or “aplurality of chambers,” without other modifiers, typically means atleast two chambers).

In those instances where a phrase such as “at least one of A, B, and C,”“at least one of A, B, or C,” or “an [item] selected from the groupconsisting of A, B, and C,” is used, in general such a construction isintended to be disjunctive (e.g., any of these phrases would include butnot be limited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, or A, B, and C together,and may further include more than one of A, B, or C, such as A₁, A₂, andC together, A, B₁, B₂, C₁, and C₂ together, or B₁ and B₂ together). Itwill be further understood that virtually any disjunctive word or phrasepresenting two or more alternative terms, whether in the description,claims, or drawings, should be understood to contemplate thepossibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

The herein described aspects depict different components containedwithin, or connected with, different other components. It is to beunderstood that such depicted architectures are merely examples, andthat in fact many other architectures can be implemented which achievethe same functionality. In a conceptual sense, any arrangement ofcomponents to achieve the same functionality is effectively “associated”such that the desired functionality is achieved. Hence, any twocomponents herein combined to achieve a particular functionality can beseen as “associated with” each other such that the desired functionalityis achieved, irrespective of architectures or intermedial components.Likewise, any two components so associated can also be viewed as being“operably connected,” or “operably coupled,” to each other to achievethe desired functionality. Any two components capable of being soassociated can also be viewed as being “operably couplable” to eachother to achieve the desired functionality. Specific examples ofoperably couplable include but are not limited to physically mateable orphysically interacting components or wirelessly interactable orwirelessly interacting components.

With respect to the appended claims, the recited operations therein maygenerally be performed in any order. Also, although various operationalflows are presented in a sequence(s), it should be understood that thevarious operations may be performed in other orders than those which areillustrated, or may be performed concurrently. Examples of suchalternate orderings may include overlapping, interleaved, interrupted,reordered, incremental, preparatory, supplemental, simultaneous,reverse, or other variant orderings, unless context dictates otherwise.Use of “Start,” “End,” “Stop,” or the like blocks in the block diagramsis not intended to indicate a limitation on the beginning or end of anyoperations or functions in the diagram. Such flowcharts or diagrams maybe incorporated into other flowcharts or diagrams where additionalfunctions are performed before or after the functions shown in thediagrams of this application. Furthermore, terms like “responsive to,”“related to,” or other past-tense adjectives are generally not intendedto exclude such variants, unless context dictates otherwise.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

What is claimed is:
 1. A method comprising: detecting an atmosphericvariation indicative of a present or possible future noise generationstate of a rotating rotor blade having a controllable feature andattached to a rotor hub driving an electric generator, the controllablefeature configured to decrease a noise generated by the rotating rotorblade if activated; selecting a noise mitigation measure responsive tothe detected atmospheric variation and in compliance with a minimumelectric power generation requirement assigned to the electricgenerator; and activating the controllable feature of the rotating rotorblade in response to the selected noise mitigation measure.
 2. Themethod of claim 1, wherein detecting the atmospheric variation includesdetecting a present wind speed.
 3. The method of claim 1, whereindetecting the atmospheric variation includes predicting a future windspeed.
 4. The method of claim 1, wherein detecting the atmosphericvariation includes detecting the atmospheric variation upwind of therotor hub.
 5. The method of claim 4, wherein detecting the atmosphericvariation includes detecting the atmospheric variation at least onerotor blade length upwind of the rotor hub.
 6. The method of claim 1,wherein detecting the atmospheric variation includes detecting theatmospheric variation downwind of the rotor hub.
 7. The method of claim1, wherein the detected atmospheric variation includes a change in windspeed, a change in wind direction, a wind gradient, a change inturbulence, a change in temperature, a change in pressure, a change inair moisture content, or a change in air density.
 8. The method of claim1, wherein the detected atmospheric variation is transient.
 9. Themethod of claim 1, wherein the controllable feature includes anairflow-modifiable region of the rotor blade located at a portion of alongitudinal length of the rotor blade.
 10. The method of claim 9,wherein the noise mitigation measure includes changing a cross-sectionalshape of the airflow-modifiable region of the rotor blade.
 11. Themethod of claim 9, wherein the noise mitigation measure includescontrolling airflow over the airflow-modifiable region.
 12. The methodof claim 9, wherein the noise mitigation measure includes dynamicallyaltering airflow over the airflow-modifiable region.
 13. The method ofclaim 9, wherein the noise mitigation measure includes releasing airfrom the airflow-modifiable region.
 14. The method of claim 9, whereinthe noise mitigation measure includes creating a transpiration airflowthrough the airflow-modifiable region.
 15. The method of claim 1,wherein the controllable feature includes a controllable rotor bladepitch.
 16. The method of claim 15, wherein the noise mitigation measureincludes changing the pitch of the rotor blade.
 17. The method of claim1, wherein selecting the noise mitigation measure includes selecting thenoise mitigation measure from at least two possible noise mitigationmeasures responsive to the detected atmospheric variation.
 18. A systemcomprising: a wind turbine including a rotor blade having a controllablefeature and attached to a rotor hub drivingly coupled to an electricgenerator, the controllable feature configured, if activated, todecrease a noise generated by the rotor blade and correspondingly todecrease electric power generated by the electric generator; a sensorconfigured to detect an atmospheric variation indicative of a present orpossible future noise generation state of the rotor blade; and acontroller circuit configured to select a noise mitigation measureresponsive to the detected atmospheric variation and in compliance witha minimum electric power generation requirement assigned to the windturbine, and further configured to activate the controllable feature inresponse to the selected noise mitigation measure.
 19. The system ofclaim 18, wherein the detected atmospheric variation is a variation inwind speed, wind direction, wind gradient, turbulence, temperature,pressure, air moisture content, or air density.
 20. The system of claim18, wherein the detected atmospheric variation is transient.
 21. Thesystem of claim 18, wherein the detected atmospheric variation is upwindof the rotor hub.
 22. The system of claim 18, wherein the detectedatmospheric variation is downwind of the rotor hub.
 23. The system ofclaim 18, wherein the controllable feature includes anairflow-modifiable region of the rotor blade located at a portion of alongitudinal length of the rotor blade.
 24. The system of claim 23,wherein the noise mitigation measure includes changing a cross-sectionalshape of the airflow-modifiable region of the rotor blade.
 25. Thesystem of claim 23, wherein the noise mitigation measure includescontrolling airflow over the airflow-modifiable region.
 26. The systemof claim 23, wherein the noise mitigation measure includes dynamicallyaltering airflow over the airflow-modifiable region.
 27. The system ofclaim 23, wherein the noise mitigation measure includes releasing airfrom the airflow-modifiable region.
 28. The system of claim 23, whereinthe noise mitigation measure includes creating a transpiration airflowthrough the airflow-modifiable region.
 29. The system of claim 18,wherein the controllable feature includes a controllable rotor bladepitch.
 30. The system of claim 29, wherein the selected noise mitigationmeasure includes changing the pitch of the rotor blade.
 31. The systemof claim 18, wherein the controller circuit is configured to select thenoise mitigation measure from at least two possible noise mitigationmeasures responsive to the detected atmospheric variation.